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Eggs usually hatch in 12-14 days at prevailing
water temperatures but can hatch in 4-5 days 64° - 68°F (17.8°-20°C).
At hatching, the young are 6-8 mm in length. They remain inactive, often
attached to vegetation by means of adhesive glands on the head, for 6-10
days, and feed on the stored yolk. Growth is very rapid, by the end of
a month they are 1¾ inches (43 mm) in length and 6 inches
(152 mm) by the end of the first summer. growth in length continues rapidly
for the first 1-3 years. Growth in length slows after sexual maturity is
attained, but increase in weight rises. Growth is extremely variable from
place to place over the extensive range depending of length of growing
season, water temperature, and availability of food. many recent studies
of growth and age determination by scales demonstrated that age interpretation
is made very difficult as a result of local conditions, rate of growth,
circuli number and presence of several types of false annuli. |
Opercular bones and possibly other cranial investing bones may give
more reliable results. There is a decrease in growth rate northward and
a corresponding increase in longevity. Females grow faster than males in
the south but this trait is not as apparent in the north. However, females
over the whole range live longer and achieve a greater maximum size
than males. There is a corresponding northward and sexual difference in
age at attainment of sexual maturity. In the south of Canada, females mature
at 3-4 and males at 2-3 years of age whereas in the north it is age 6 for
females and age 5 for males. Life expectancy in fast-growing southern Canadian
populations can be as low as 10-12 years and in slow growing arctic populations
as high as 24-26 years.
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